The present invention relates to a device for locking an electrical device to an accessory part.
Locking devices of this type are used, for example, to reliably connect cordless hand-guided power tools to a battery pack used as a power supply.
The known locking devices usually have a linear guide provided on the power tool into which the battery pack is slid until, after being slid all the way in, it comes into contact with a stop and is locked in this position in relation to the power tool, while simultaneously producing an electrical connection between a battery of the battery pack and an electrical circuit of a consumer of the power tool. The locking usually occurs with the aid of a latch, which is supported in a housing of the power tool so that it can move in opposition to the force of a spring and which the spring force brings into engagement with a detent recess in the battery pack. A release mechanism is used to release the connection and usually has a push button, which is situated in the region of the guide and is manually actuated in order to disengage the latch from the detent recess and release the battery pack. The battery pack is then slid along the guide into a removal position in which it no longer engages the electrical device.
Since the movement resistance while the battery pack is being slid into the guide of the power tool generally increases toward the end of the insertion path due to the increasing size of the friction surfaces and due to the contact between the electrical terminals, the user can be given the impression that the two components are properly locked in position although this is not yet the case. This can result in the battery pack slipping out of the guide during transport or operation of the power tool when the latter is tilted downward toward the removal position, which can lead to property damage or injury.
In order to prevent the battery pack from unintentionally detaching from the power tool, some of the applicant's larger and heavier power tools are already provided with a two-stage locking device called a double locking mechanism in which, as the battery pack is slid into the guide, the spring force of a spring-loaded latch brings it into engagement with two detent recesses provided in the battery pack, one after the other in the insertion direction. When the latch engages with the first detent recess, the battery pack is only secured in relation to the power tool, whereas an electrical connection is only produced when the latch engages in the second detent recess.
This does make it possible to prevent the battery pack from unintentionally detaching from the power tool when the latch is not engaging in the second detent recess or is not properly engaging in it, for example because the user has not slid the battery pack all the way into the locking position in the guide. But if the user does not hold the battery pack while actuating the release mechanism and the guide is simultaneously pointing obliquely downward from the locking position, then even a two-stage locking mechanism is unable to reliably prevent the battery pack from falling out.